1. Field of the Invention
The invention relates to a fastener driver, more particularly to a hammer-drive powder-actuated tool.
2. Description of the Related Art
Referring to FIG. 1, a conventional hammer-drive powder-actuated tool 1 is shown to include a tubular housing 11 having a front open end 111 and an enlarged rear open end 112, a barrel unit 12 inserted movably into the housing 11 via the front open end 111 of the housing 11, a piston assembly 14 disposed movably in the barrel unit 12, a sleeve 13 coupled to a rear end of the barrel unit 12 and defining a chamber 131 for receiving powder load therein, a firing pin holder 15 disposed in the housing 11, abutting against the sleeve 13 and having a through hole 151, a firing pin 16 mounted movably in the through hole 151 and operable between a normal position and a firing position, and a compressed spring 17 sleeved on the firing pin 16 for biasing the firing pin 16 to move toward the normal position and for providing a desired preset biasing force (normally more than 60 lbs.) on the firing pin 16 at the normal position.
The firing pin 16 includes a pin body 161 and a nut 162. The pin body 161 is in the form of a bolt. The pin body 161 has an enlarged firing end portion 1611 disposed adjacent to the sleeve 13, spaced apart from the powder load in the chamber 131 in the sleeve 13 when the firing pin 16 is at the normal position, as shown in FIG. 1, and contacting and igniting the powder load in the chamber 131 in the sleeve 13 when the firing pin 16 is at the firing position, and a threaded end portion 1612 opposite to the firing end portion 1611 and disposed adjacent to the rear open end 112 of the housing 11. The nut 162 is connected threadedly to the threaded end portion 1612 of the pin body 161. A positioning pin 163 extends radially through the nut 162 and the threaded end portion 1612 of the pin body 161 so as to prevent movement of the nut 162 relative to the threaded end portion 1612 of the pin body 161. The compressed spring 17 has opposite ends abutting respectively against the nut 162 and an inwardly extending shoulder portion 152 of an inner annular surface defining the through hole 151. In use, the firing pin 16 is moved from the normal position to the firing position through beating by a hammer with a sufficient force which can overcome the preset biasing force of the spring 17 on the threaded end portion 1612 of the pin body 161.
It is noted that, in order to prevent rotation of the pin body 161 with the nut 162 when screwing the nut 162 onto the pin body 161 during assembly, the firing end portion 1611 of the pin body 161 is shaped as a polygon, such as a hexagon, such that the through hole 151 has a polygonal hole portion 1511, such as a hexagonal hole section, corresponding to the firing end portion 1611. As a result, the firing pin holder 15 cannot be formed by lathe due to a relatively complicated configuration thereof. Furthermore, the firing pin holder 15 is riveted to the housing 11, meanwhile, each of the nut 162 and the threaded end portion 1612 of the pin body 161 must be formed with a through hole (not shown) for permitting extension of the positioning pin 163 there through. Therefore, the conventional powder-actuated tool 1 is fabricated at a relatively high cost. Moreover, since the compressed spring 17 is positioned in the housing 11 through engagement between the nut 162 and the threaded end portion 1612 of the pin body 161, and insertion of the positioning pin 163 into the nut 162 and the threaded end portion 1612 of the pin body 161, it takes a relatively long period of time during assembly.